U.S. patent number 4,315,970 [Application Number 06/189,433] was granted by the patent office on 1982-02-16 for adhesion of metals to solid substrates.
This patent grant is currently assigned to Dow Corning Corporation. Invention is credited to James B. McGee.
United States Patent |
4,315,970 |
McGee |
February 16, 1982 |
**Please see images for:
( Certificate of Correction ) ** |
Adhesion of metals to solid substrates
Abstract
What is disclosed is a method of improving the adhesion of thin
metal coatings to various solid substrates by pretreatment of the
solid substrates using organofunctional silanes or mixtures of
organofunctional silanes with organosilanes and thereafter
depositing metals to form films or coatings.
Inventors: |
McGee; James B. (Sanford,
MI) |
Assignee: |
Dow Corning Corporation
(Midland, MI)
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Family
ID: |
26818149 |
Appl.
No.: |
06/189,433 |
Filed: |
September 22, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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120197 |
Feb 11, 1980 |
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Current U.S.
Class: |
428/412; 427/164;
427/166; 427/167; 427/387; 427/404; 427/407.2; 428/425.8; 428/429;
428/447 |
Current CPC
Class: |
C09D
4/00 (20130101); C09D 183/04 (20130101); C09J
5/00 (20130101); C09D 4/00 (20130101); C08G
77/22 (20130101); C09D 4/00 (20130101); C08G
77/04 (20130101); Y10T 428/31605 (20150401); Y10T
428/31507 (20150401); Y10T 428/31663 (20150401); Y10T
428/31612 (20150401) |
Current International
Class: |
C09J
5/00 (20060101); C09D 4/00 (20060101); C09D
183/04 (20060101); B32B 015/08 (); B32B
017/10 () |
Field of
Search: |
;428/447,429,412
;427/387,164,167,166,404,407.2,162,389.8,407.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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52-16586 |
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Feb 1977 |
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JP |
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51-73273 |
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Aug 1976 |
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JP |
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1550532 |
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Aug 1979 |
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GB |
|
Primary Examiner: Kendall; Ralph S.
Attorney, Agent or Firm: McKellar; Robert L.
Parent Case Text
BACKGROUND OF THE INVENTION
This application is a continuation-in-part of application Ser. No.
120,197, filed Feb. 11, 1980 abandoned.
Claims
That which is claimed is:
1. A method of forming an adherent metal surface on a substrate
by
(I) treating a solid substrate with at least one
organofunctionalsilane, or the partial hydrolyzates thereof, having
the general formula ##STR13## or a mixture of an organofunctional
silane or the partial hydrolyzates thereof with a different
organosilane, or the partial hydrolyzates thereof, which has the
general formula
in which formulae R is an alkyl radical of 1-4 carbon atoms, R' is
a difunctional hydrocarbon radical having from 1-12 carbon atoms or
a --CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 --radical X is
an --NH.sub.2, ##STR14## --SH, OH or Cl radical, R" is an --(R'X)
radical, a and b each have a value of 2 or 3, c has a value of 0 or
1 and a+c=3;
(II) drying the silane treated surface until the majority of
volatile materials have been removed and thereafter,
(III) vapor depositing a metal on the silane treated surface to
form a thin continuous film or coating thereon.
2. A method as claimed in claim 1 wherein the organofunctional
silane is (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 SH.
3. A method as claimed in claim 1 wherein the organofunctional
silane is ##STR15## and the organosilane is (CH.sub.3 O).sub.3
Si(CH.sub.2).sub.3 SH.
4. A method as claimed in claim 3 wherein the weight ratio of the
organofunctional silane to organosilane is 1:1.
5. A method as claimed in claim 1 wherein in step I, the
organofunctional silane and organosilane are partial
hydrolyzates.
6. A method as claimed in claim 5 wherein the partial hydrolyzates
are present at 0.1 to 10 weight percent based on the weight of
solvent, water and silanes present.
7. A method as claimed in claim 6 wherein the partial hydrolyzates
are present at 0.5-2.5 weight percent based on the weight of
solvent, water and silanes present.
8. A method as claimed in claim 1 wherein in step III, the metal
deposited is selected from a group consisting of copper, nickel,
tin, silver, silver solder, gold, aluminum, platinum, titanium,
zinc and chrome.
9. A method as claimed in claim 8 wherein the metal deposited is
silver.
10. A method as claimed in claim 8 wherein the metal deposited is
aluminum.
11. A method as claimed in claim 8 wherein the metal deposited is
chrome.
12. A method as claimed in claim 8 wherein the metal deposited is
nickel.
13. A method as claimed in claim 8 wherein the metal deposited is
copper.
14. A method as claimed in claim 8 wherein the metal deposited is
gold.
15. A method as claimed in claim 8 wherein the metal deposited is
silver solder.
16. A method as claimed in claim 1 wherein the substrate is
selected from a group consisting of plastics, wood, cardboard,
glass, metals, silicone rubbers and silicone resins.
17. A method as claimed in claim 16 wherein the substrate is
glass.
18. A method as claimed in claim 16 wherein the substrate is
plastic.
19. A method as claimed in claim 16 wherein the substrate is
metal.
20. A method as claimed in claim 17 wherein the glass is float
glass.
21. A method as claimed in claim 18 wherein the plastic is
polycarbonate.
22. A method as claimed in claim 18 wherein the plastic is
acrylic.
23. A method as claimed in claim 18 wherein the plastic is
nylon.
24. A method as claimed in claim 18 wherein the plastic is an
acrylonitrile-butadiene-styrene copolymer.
25. A method as claimed in claim 18 wherein the plastic is
polyethylene.
26. A method as claimed in claim 18 wherein the plastic is
crosslinked polyethylene.
27. A method as claimed in claim 19 wherein the substrate is
aluminum.
28. A method as claimed in claim 19 wherein the substrate is
steel.
29. A method as claimed in claim 21 wherein the polycarbonate is in
the form of a lens.
30. A method as claimed in claim 21 wherein the polycarbonate is in
the form of a flat sheet.
31. A method as claimed in claim 21 wherein the polycarbonate is in
the form of a thermoformed sheet.
32. A method as claimed in claim 22 wherein the acrylic is in the
form of a lens.
33. A method as claimed in claim 22 wherein the acrylic is in the
form of a flat sheet.
34. A method of forming an adherent metal surface on a substrate
by
(I) treating a solid substrate with a curable organic or silicone
basecoat and curing said basecoat;
(II) treating said cured basecoat with at least one
organofunctional silane, or the partial hydrolyzates thereof,
having the general formula ##STR16## or a mixture of an
organofunctional silane or the partial hydrolyzates thereof with a
different organosilane, or the partial hydrolyzates thereof, which
has the general formula
in which formulae R is an alkyl radical of 1-4 carbon atoms, R' is
a difunctional hydrocarbon radical having from 1-12 carbon atoms or
a --CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 -- radical, X is
an --NH.sub.2, ##STR17## --SH, OH or Cl radical, R" is an --(R'X)
radical, a and b each have a value of 2 or 3, c has a value of 0 or
1 and a+c=3;
(III) drying the silane treated surface until the majority of
volatile materials have been removed and thereafter,
(IV) vapor depositing a metal on the silane treated surface to form
a thin continuous film or coating thereon.
35. A method as claimed in claim 34 in which the curable organic
basecoat is a curable acrylic polymer.
36. A method as claimed in claim 34 in which the curable organic
basecoat is a curable polyester polymer.
37. A method as claimed in claim 34 in which the curable organic
basecoat is a curable polyurethane polymer.
38. A method as claimed in claim 34 in which the curable organic
basecoat is a curable epoxy polymer.
39. A method as claimed in claim 34 in which the curable organic
basecoat is a curable silicone-epoxy copolymer.
40. A method as claimed in claim 34 in which the curable silicone
basecoat is a silicone elastomer.
41. A method as claimed in claim 34 in which the curable silicone
basecoat is a silicone resin.
42. A method as claimed in claim 41 wherein the curable silicone
basecoat is a silicone resin which is a pigment-free aqueous
coating composition comprising a dispersion of colloidal silica in
lower aliphatic alcohol-water solution of the partial condensate of
a silanol of the formula RSi(OH).sub.3 in which R is selected from
the group consisting of alkyl radicals of 1 to 3 inclusive carbon
atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the
gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl
radical, at least 70 weight percent of the silanol being CH.sub.3
Si(OH).sub.3, said composition containing 10 to 50 weight percent
solids consisting essentially of 10 to 70 weight percent colloidal
silica and 30 to 90 weight percent of the partial condensate, said
composition containing sufficient acid to provide a pH in the range
of 3.0 to 6.0.
43. A method of forming an adherent metal surface on a substrate
by
(I) treating a solid substrate with a curable organic or silicone
basecoat which contains at least one organofunctional silane, or
the partial hydrolyzate thereof, having the general formula
##STR18## or a mixture of an organofunctional silane, or the
partial hydrolyzate thereof, with a different organosilane, or the
partial hydrolyzate thereof, which has the general formula
in which formulae R is an alkyl radical of 1-4 carbon atoms, R' is
a difunctional hydrocarbon radical having from 1-12 carbon atoms or
a --CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 -- radical, X is
an --NH.sub.2, ##STR19## --SH, OH or Cl radical, R" is an --R'X)
radical, a and b each have a value of 2 or 3, c has a value of 0 or
1 and a+c=3;
(II) drying the basecoat until the majority of volatiles have been
removed and thereafter;
(III) vapor depositing a metal on the basecoat to form a thin
continuous film or coating thereon.
44. The method of claim 1 wherein there is also present a clear
topcoat on the vapor deposited metal surface.
45. A method as claimed in claim 34 wherein there is also present a
clear topcoat on the vapor deposited metal surface.
46. A method as claimed in claim 43 wherein there is also present a
clear topcoat on the vapor deposited metal surface.
47. An article prepared by the method of claim 43 wherein the
substrate is glass, the organofunctional silane is ##STR20## the
organosilane is (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 SH, the ratio
of organofunctional silane to organosilane is 1:1, the silanes are
used as a 2.5 weight percent water-alcohol solution and the vapor
deposited metal is silver.
48. The article as claimed in claim 47 wherein the article is
further topcoated with a clear, cured, protective coating.
49. An article prepared by the method of claim 1.
50. An article prepared by the method of claim 34.
51. An article prepared by the method of claim 42.
52. An article prepared by the method of claim 43.
53. The methods as claimed in claims 1, 34 or 43 wherein the solid
substrate is primed with an adhesion promoter.
54. An article as claimed in claims 47, 48, 49, 50, 51 or 52
wherein the article is primed with an adhesion promoter.
Description
There are many applications where it is desirable to form thin
metallic films or coatings on various solid substrates. An example
of such an application is the formation of silvered mirrors wherein
very thin films or coatings of silver metal are deposited from
chemical solution onto glass or similar substrates. Also, large
reflectors for solar applications have been formed from vapor
deposited silver or aluminum on solid substrates.
Some of the problems associated with prior art methods of forming
thin metallic coatings on solid substrates have been the cumbersome
application methods, for example, in producing silvered mirrors
from chemical solution and, the inability to retain the metallic
coating on the solid substrate for long periods of time. Also, in
vapor deposition, vacuum metallizing, ion plating, spraying and
similar methods, the metallized surface can only retain its
aesthetic value of the substrate has been pre-treated with some
composition which can mask or eliminate the scratches, pits and
voids in the solid substrate. Such materials are generally curable
organic coatings which are first coated onto the solid substrates
at such thicknesses that they will physically fill the scratches,
pits and voids, and are then cured. The metallizing is then carried
out on the surface of the organic coating. Unfortunately, because
of the presence of these organic "basecoats", the manufacturer is
faced with a variety of adhesion problems between the basecoats and
the solid substrate and the basecoat and the thin metallic film or
coating. This problem is enhanced considerably when the
manufactured item is intended to be used outdoors and is subject to
the ravages of the weather.
What is needed therefore is an improved method of forming adherent
metallic films or coatings on solid substrates and improved
metallic coated materials.
According to the present invention there is disclosed an improved
method of adhering a thin metallic film or coating to a solid
substrate. The improved method utilizes a specific silane or
mixtures of silanes to strongly adhere the thin metallic film or
coating to solid substrates.
It has been known for a number of years that silanes are useful for
bonding many materials to many various surfaces. It is generally
recognized that silane coupling agents are not universal coupling
agents such that any given silane will bond all materials to all
substrates. Instead, it is generally accepted that specific silanes
can be used for adhesion of specific materials to specific
substrates, that is, the silane must be matched to the application
and it cannot be assumed that all silanes will work in all
applications.
In a recent British Pat. No. 1,550,532, issued Aug. 15, 1979, it is
disclosed that thin films or coatings of metals can be adhered to
plastic substrates by the use of a combination of alkoxysilanes,
alkylsilicates and copolymers of alkyl acrylate or alkyl
methacrylate with hydroxyalkyl acrylates or hydroxyalkyl
methacrylates. This patent discloses that the inventive composition
therein serves two purposes i.e. the polymeric material is a film
former and the silane enhances adhesion of metal overcoat. The
alkoxy silanes shown there are of the formula R.sub.n
Si(OR').sub.4-n wherein n is 1, 2 or 3, R' is a C.sub.1 -C.sub.6
hydrocarbon group and R' is a C.sub.1 -C.sub.4 alkyl group. This
prior art material and method appears to work quite well as long as
articles for use indoors are contemplated. It has been observed
that this material does not have adequate adhesion of the deposited
metal to the polymeric film which results in loss of adhesion of
the thin metallic film.
It has now been found that the adhesion of thin metal films to
various substrates can be enhanced by the use of certain silanes
and silane mixtures on certain substrates such that the articles
prepared using the inventive method are durable, weatherable and
have brilliance and enhanced specularity.
THE INVENTION
What is disclosed herein is a method of forming an adherent
continuous thin metal surface on a substrate and the articles
prepared thereby.
Thus, what is disclosed is a method of forming an adherent metal
surface on a substrate by (I) treating a solid substrate with at
least one organofunctional silane, or the partial hydrolyzate
thereof, having the general formula ##STR1## or a mixture of an
organofunctional silane or the partial hydrolyzate thereof with a
different organosilane, or the partial hydrolyzate thereof, which
has the general formula (RO).sub.b SiR".sub.4-b in which formulae R
is an alkyl radical of 1-4 carbon atoms, R' is a difunctional
hydrocarbon radical having from 1-12 carbon atoms or a
radical, X is an --NH.sub.2, ##STR2## --SH, OH or Cl radical, R" is
an --(R'X) radical, a and b each have a value of 2 or 3, c has a
value of 0 or 1 and a+c=3; (II) drying the silane treated surface
until the majority of volatile materials have been removed and
thereafter, (III) depositing a metal on the silane treated surface
to form a thin continuous film or coating thereon.
The organofunctionalsilanes used in step I have the general formula
##STR3## wherein R is an alkyl radical of 1-4 carbon atoms, R' is a
difunctional hydrocarbon radical having from 1-12 carbon atoms or
a
radical, X is an --NH.sub.2, ##STR4## --SH, OH or Cl radical. R is
preferably the methyl radical. a has a value of 2 or 3. c has a
value of 0 or 1 and a+c=3. Thus, contemplated within the scope of
the formula ##STR5## are such organofunctional silanes as
##STR6##
It should be noted that contemplated within the scope of this
invention are the partial hydrolyzates of these organofunctional
silanes. By "partial hydrolyzate", the inventor herein means the
water soluble or water miscible product formed when the
organofunctional silane is treated with water to hydrolyze all or a
part of the alkoxy groups on the molecule. Sometimes, in order to
effect the hydrolysis, a small amount of acid is required along
with the water. Whenever "hydrolyzate" or "partial hydrolyzate" is
used herein, it shall mean that it contains the hydrolyzed silane
or silanes, water for hydrolysis and the alcohol solvent formed by
the cleavage of the alkoxy groups from the silane.
The treatment of the substrate can be carried out with the
organofunctional silane or its partial hydrolyzate alone but
contemplated within the scope of this invention is a mixture of the
organofunctional silane or its partial hydrolyzate with a different
organosilane having the general formula (RO).sub.b SiR".sub.4-b
wherein R has the same meaning as R above, R" can be an --(R'X)
radical and b has a value of 2 or 3. As indicated above for the
formula ##STR7## the partial hydrolyzates of (RO).sub.b
SiR".sub.4-b are also part of this invention. R is preferably
methyl.
The organofunctional silanes and the organosilanes are well-known
commercial silanes and it is believed that their manufacture is
adequately set out in the art and need not be repeated herein.
Whenever it is required to use a mixture of the silanes, it is done
by a simple mixing technique. The neat silanes can be mixed first
then cohydrolyzed or they can be hydrolyzed separately and the
hydrolyzates mixed thereafter.
For purposes of this invention, whenever a mixture of silanes is
required, it is generally preferred that they be mixed in a ratio
of 1:10 to 10:1 organofunctional silane to organosilane on a weight
basis. The ratio applies to the weight of the silanes before
hydrolysis.
As indicated above, some of the silanes require the presence of a
small amount of acid to enhance hydrolysis. Such acids are, for
example, hydrochloric and acetic. This acid requirement is
well-known in the silane hydrolysis art.
It is generally preferred that the silanes be hydrolyzed prior to
mixing. After the silanes are hydrolyzed, simple hand shaking of
the hydrolysis vessel i.e. a bottle or flask will suffice to force
the hydrolysis reaction. Generally, the hydrolysis mixture is used
at this point without further modification or purification.
The amount of total silane in the hydrolysis mixture can be from
0.01 to 35 weight percent.
Whenever the silanes are to be used neat, they can be dissolved in
solvents which are soluble with or miscible with water such as
isopropanol, methanol, butanol, methylcellosolve or the like.
Mixtures of such types of solvents are contemplated within the
scope of this invention. these solvents can also be used with the
hydrolyzed silanes to enhance film forming abilities, etc.
The silanes or silane solutions can be applied to the substrate by
any method which is convenient for the user. Such methods as
dipping, flowing and spraying are most satisfactory for this
invention.
The substrates useful in this invention are those which are solid
substrates. Thus, most every useful solid substance which makes up
an article can be the substrate of this invention. Such substrates
can be, for example, plastics such as
acrylonitrile-butadiene-styrene copolymers, Sioplas.RTM.
crosslinked polyethylene, polycarbonates, polyethylene
terephthalates such as Mylar.RTM., polyimides such as Kapton.RTM.,
polyphenylene oxides such as Noryl.RTM., polyphenylene sulfides
such as Ryton.RTM. and mineral filled nylons such as Minlon.RTM.,
acrylics, urethanes, epoxys and polyesters, just to name a few.
Wood, cardboard, glass, metals, silicone rubbers and resins,
urethane foams and polyvinylchloride foams are examples of other
useful substrates.
One method taught herein consists of treating a solid substrate
with an organofunctional silane or a mixture of an organofunctional
silane and an organosilane and then allowing the silane treated
surface to dry until the majority of the volatile materials have
been removed from the treated surface. What is meant by volatile
materials are the solvents, water and low molecular weight products
that have been formed upon hydrolysis. What is meant by the
"majority" of volatile materials is that the surface should be tack
free or nearly tack free to the finger touch. This can be
accomplished in a number of ways. For example, the treated surfaces
can be left at room temperature for a period of time, perhaps days,
to allow slow evaporation of the volatile materials into the
atmosphere. Since time is usually a factor in commercial
manufacture, however, the articles can be heated to remove
volatiles. Vacuum can be applied to reduce the pressure and enhance
volatization. The inventor herein has used a number of methods to
cause the removal of volatiles in a short period of time, such as
1-5 seconds, by heating and applying vacuum simultaneously.
Any method of volatile material removal that fits the manufacturers
mode of manufacture is contemplated herein.
After the volatile materials are removed, the thin metal coating is
applied. Generally, any method by which thin, continuous metal
coatings can be applied will suffice for this invention. Methods
such as vapor deposition, electroplating, sputtering, ion plating
and spraying are preferred. However, applying the thin, continuous
metal coating can be accomplished from current methods of chemical
solution application without detrimental affects on the adhesion
promoting coating.
Metals that are useful in this invention are any metals that can be
vapor deposited, electroplated, sputtered, ion plated, sprayed or
applied from chemical solution. Such metals as copper, nickel, tin,
silver, silver solder, gold, aluminum, platinum, titanium, zinc and
chrome are preferred.
For purposes of this invention "thin" means the thickness of the
metal film that is required to give a continuous, coherent film or
coating. Generally, these coatings are less than 30 microns
thick.
The articles prepared in this invention can be covered by clear
protective coatings such as the silicone resins set forth in U.S.
Pat. No. 3,986,997. These materials are generally referred to as
"topcoats" and are well-known in the art.
As indicated earlier, the surfaces of some substrates are soft
enough that they are blemished by gouges or scratches during the
manufacture of the article and in order to end up with a product
that is aesthetically pleasing, the blemishes must be eliminated
since simple metal plating over them with thin coatings or films
allows the blemishes to show through.
A common method of covering over the blemishes is to basecoat the
substrate with a material such as curable organic polymers. The
organic polymer fills the blemishes and gives a smooth, flat,
blemish free surface over which the thin metal coating can be
applied.
Another invention herein therefore contemplates the use of such
basecoat materials in conjunction with the method of, and materials
of, this invention. Thus, this invention also deals with the
treatment of a substrate with a basecoat and the application of the
silane or silanes of this invention to said basecoat. The metal is
then applied to the silane treated basecoat. Preferred for this
invention are certain silicone basecoats. More specifically, the
preferred basecoat is one that is selected from the siloxane
coatings disclosed in U.S. Pat. No. 3,986,997 issued to Harold A.
Clark Oct. 19, 1976. The siloxane coatings disclosed in that patent
are herein incorporated by reference.
In using a base coat, the substrate is cleaned by any conventional
process and then the basecoat is applied and cured. Generally, for
the Clark coating, 6-8 hours at 150.degree. C. is required. Some
basecoats require only a few minutes air dry time. In certain
circumstances, depending on the substrate and the basecoat, a
primer may be required. The silanes of this invention, for example,
could be used as such primers. The cured basecoat is then top
treated with the silane or mixtures of silanes, dried, then
overcoated with the metal of choice. Thus, contemplated within the
scope of the claims of this invention are substrates named herein
overcoated with organic or silicone basecoats and then treated with
the inventive silanes or silane mixtures.
A third aspect of this invention is the use of the silanes of this
invention in conjunction with certain curable coatings to enhance
the adhesion of the thin metal films or coatings. Whereas, the
essence of this invention where first presented herein is the
treatment of certain substrates or the treatment of certain
substrates basecoated with organic or silicone curable coatings,
this further aspect of this invention deals with the metal coating
of curable organic or silicone basecoats which have included in
them, before cure, the inventive silane or silanes disclosed
herein.
This invention therefore also consists of incorporating in the
curable basecoat, the silanes of this invention and then depositing
metals to form films or coatings thereon. The invention therefore
also consists of a method of forming an adherent metal surface on a
substrate by (I) treating a solid substrate with a curable organic
or silicone basecoat which contains at least one organofunctional
silane, or the partial hydrolyzate thereof, having the general
formula ##STR8## or a mixture of an organofunctional silane, or the
partial hydrolyzate thereof, with a different organosilane, or the
partial hydrolyzate thereof, which has the general formula
(RO).sub.b SiR".sub.4-b in which formulae R is an alkyl radical of
1-4 carbon atoms, R' is a difunctional hydrocarbon radical having
from 1-12 carbon atoms or a --CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2
CH.sub.2 -- radical, X is an --NH.sub.2, ##STR9## --SH, OH or Cl
radical, R" is an --(R'X) radical, a and b each have a value of 2
or 3, c has a value of 0 or 1 and a+c=3; (II) drying the basecoat
until the majority of volatiles have been removed and thereafter;
(III) depositing a metal on the basecoat to form a thin continuous
film or coating thereon.
The organic basecoats useful herein are those currently being used
as basecoats for metal deposition on solid articles. These
materials are air dry acrylics or urethanes which can be used with
or without heat cure. Such a material, for example, is EB-1, an
acrylic polymer manufactured by Red Spot Paint and Varnish Co.,
Inc, Evansville, Ind.
The amount of silane or silanes incorporated in the basecoat is 0.1
to 10 weight percent based on the weight of silane(s) and basecoat.
Simple mixing of the silane into the basecoat is all that is
required. It should be noted that such mixing need not be done
under anhydrous conditions as the adhesive effect is enjoyed
whether the silanes are used neat or in the pre-hydrolyzed
condition. The basecoat is dried and/or cured, depending on the
application where it is being used, and then the metal top coat is
applied by one of the methods indicated earlier.
Articles which are manufactured by the methods of the inventions
herein have enhanced adhesion, weathering, durability and enhanced
efficiency and specularity whenever the metal surface is a mirrored
surface.
The following examples are not to be construed as limiting the
invention which is set forth in the claims.
Several silanes were evaluated in this invention by observing the
adhesion of the metal coating. An appearance determination was made
which was subjective and was based upon such characteristics as
continuum of film, brilliance, specularity and the presence or
absence of voids, pockmarks and the like. An excellent film is one
which is continuous, without voids and/or pockmarks and has
brilliance and high specularity. Specularity is a term used in the
mirrored surfaces art which means the degree of light transmitted
from the surface of a mirror i.e. how good are the mirror
properties. Adhesion was measured subjectively by rubbing the metal
surface with a cloth saturated with acetone, methanol or
isopropanol using moderate pressure unless a different method is
indicated. The degree to which the metal surface survived this
treatment is reported. No removal of the coating is considered
"excellent". "Good" is when some slight abrasion occurred. "Fair"
means noticeable removal of metal. "Poor" means the removal of
essentially all of the metallic coating. "None" means all the
coating was removed.
EXAMPLE 1
The following samples were prepared to observe which silanes or
combinations of silanes would give the best enhanced adhesion
between a given substrate and certain metals. Silanes or
combinations of silanes were made at the concentrations shown by a
method which involved the hydrolysis of each silane and the
eventual combinations of the silanes to give the adhesion promoter
used on the substrate. Table I in this example shows the various
silanes tested.
Silane A is (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3
NH(CH.sub.2).sub.2 NH.sub.2. Silane B is (CH.sub.3 O).sub.3
Si(CH.sub.2).sub.3 SH. Silane C is ##STR10## Silane D is (CH.sub.3
O).sub.3 Si(CH.sub.2).sub.3 Cl, and Silane E is HO(CH.sub.2).sub.3
Si(OCH.sub.3).sub.3.
Results are on Table II. IPA is isopropanol. MeOH is methanol. gms
is grams.
PRIMER PREPARATION
Silane A (8 gms), IPA (8 gms) and 1.12 gms of water were mixed with
agitation in a small 1 ounce glass bottle with a screw-top lid. The
bottle was allowed to stand overnight (about 16-20 hrs). The
material was then diluted with 800 gms of IPA upon transferring to
a larger bottle.
Silane B (12.35 gms), IPA (717.65 gms), Glacial acetic acid (30
gms) and 40 gms of water were mixed together in the order given
herein.
Silane C (24 gms) and 1.2 gms of water were mixed together and
allowed to stand overnight (16-20 hrs). The material was then
diluted by 800 gms of MeOH.
Three gms of the Silane D was treated with 27 gms of MeOH and then
a small amount of acetic acid and enough water for complete
hydrolysis was added, the mixture was shaken until clear and then
was used without extensive aging.
E was used at 20 weight % in MeOH by using the same method as for
D.
All primers were filtered before use.
All samples were hand dipped in the primer solutions and the excess
material was allowed to drip off. The samples were then dried as
shown in the tables.
Table I shows the silanes or combination of silanes that were used
in the examples. "Sample #" is the reference number for the runs
that were carried out for these examples. "Silane #1" is the
organofunctional silane used in the sample. "Silane #2" is the
organosilane used in the sample. "Acid added" and "H.sub.2 O added"
means that the material was used as a hydrolyzate, in the
hydrolysis water, with the alcohol by-produced upon hydrolysis. In
those cases where the silane was used neat, that is without prior
hydrolysis, it is so indicated.
TABLE I ______________________________________ Sample Silane Silane
Solvent Solvent H.sub.2 O Acid # #1 #2 for #1 for #2 added added
______________________________________ 1 A -- IPA -- yes No 2 B --
IPA -- yes yes 3 C -- MeOH -- yes -- 4 C B MeOH IPA yes yes 5 A B
MeOH IPA yes yes 6 -- E -- MeOH yes --
______________________________________
In Table II, the sample # from Table I indicates the silane(s) used
in that particular run. If more than one run was made using the
same silane but a different substrate or deposited metal, the run
was designated a, b, c, etc. For example, from Table I, sample 4 is
a primer made up of silanes C and B. Table II, sample 4a shows that
the silanes were used in a ratio of 2.4:1, there was present 1.3
weight percent total silane in the primer, the substrate in the run
was glass and the deposited metal was silver solder. Sample 4b in
Table II shows the primer of sample 4 of Table I, having the same
ratio of silanes at the same weight percent solids but the
substrate is now acrylic sheet and the deposited metal is
aluminum.
All samples in Table II were vapor deposited using a Mikros Vacuum
Evaporator Model VE-10 manufactured by Thermionics Laboratories,
Hayward, CA.
TABLE II
__________________________________________________________________________
Deposited Dry/Cure Ratio of Total Weight Sample # Substrate Metal
Coating Conditions Adhesion * Silanes #1:2 % Silane(s)
__________________________________________________________________________
1 glass silver solder 30 min/30 min. Fair A -- 1 @25.degree.
C./@150.degree. C. 2 glass silver solder 30 min/30 min Excellent A
-- 1.5 @25.degree. C./@150.degree. C. 3 glass silver solder 30
min/30 min Good A -- 0.4 @25.degree. C./@150.degree. C. 4a glass
silver solder 35 min/30 min Excellent A 2.4:1 1.3 @25.degree.
C./@150.degree. C. 4b acrylic sheet Aluminum None/None Fair A 2.4:1
1.3 4c Oxford ABS Aluminum 30 min/1hr. @ Good A 2.4:1 1.3
@25.degree. C./80.degree. C. 4d Ryton-R8 Aluminum 30 min/1 hr. @
Good A 2.4:1 1.3 @25.degree. C./80.degree. C. 4e Noryl Aluminum 30
min/1 hr. @ Good A 2.4:1 1.3 @25.degree. C./80.degree. C. 4f Minlon
Aluminum 30 min/1 hr. @ Good A 2.4:1 1.3 @25.degree. C./80.degree.
C. 4g Aluminum chromium 30 min./1 hr. @ Excellent A 0.8:1 1.35
panel @25.degree. C./80.degree. C. 4h steel silver 30 min./65 min@
Excellent A 0.6:1 1.1 @25.degree. C./100.degree. C. 4i Sioplas.RTM.
Aluminum 5 min./60 min@ Excellent A 2.4:1 1.3 crosslinked
@25.degree. C./75.degree. C. polyethylene 4j polyethylene Aluminum
5 min./60 min@ Excellent A 2.4:1 1.3 @25.degree. C./75.degree. C.
4k Lexan.RTM. silver 5 min./10 min@ Excellent I 0.6:1 1.1
polycarbonate @25.degree. C./100.degree. C. 4l wood silver 60
min/38 min@ poor A 0.6:1 1.1 @25.degree. C./75.degree. C. 4m paper
silver 10 min/38 min@ good A 0.6:1 1.1 @25.degree. C./75.degree. C.
4n silicone silver 60 min/38 min Excellent A 0.6:1 1.1 circuit
board @25.degree. C./@75.degree. C. 4o silicone silver 60 min/38
min Good A 0.6:1 1.1 epoxy @25.degree. C./@75.degree. C. circuit
board 4p Teflon.RTM. cloth silver 2 min/48 min None I 0.6:1 1.1
@25.degree. C./@100.degree. C. 4q polyester silver 30 min/30 min
Excellent A 0.6:1 1.1 @25.degree. C./@100.degree. C. 4r glass
Aluminum 30 min/50 min Good A 0.8:1 1.3 @25.degree. C./@80.degree.
C. 4s glass copper 30 min/30 min Excellent A 0.8:1 1.35 @25.degree.
C./@150.degree. C. 4t glass chromium 30 min/30 min Excellent A
0.8:1 1.35 @25.degree. C./@150.degree. C. 4u glass nickel 30 min/30
min Excellent A 0.8:1 1.35 @25.degree. C./@150.degree. C. 4v glass
tin 30 min/60 min Excellent A 0.6:1 1.1 @25.degree. C./@100.degree.
C. 4w glass silver 30 min/60 min Excellent A 2.4:1 1.3 @25.degree.
C./@80.degree. C. 4x glass gold 30 sec./30 min. Excellent A 0.8:1
1.35 @25.degree. C./@100.degree. C. 2a** glass silver 30 min/10 min
Excellent A -- 10.0 @25.degree. C./120.degree. C. 2b** glass silver
30 min/10 min Good A -- 100 @25.degree. C./@120.degree. C. 2c**
glass silver 30 min/10 min Fair A -- 0.1 @25.degree.
C./@120.degree. C. 2d** glass silver 30 min/10 min Fair A -- 0.01
@25.degree. C./@120.degree. C. 3a** glass silver 30 min/10 min.@
Good A -- 100.0 @25.degree. C./120.degree. C. 3b** glass silver 30
min/10 min.@ Good A -- 10.0 @25.degree. C./120.degree. C. 3c**
glass silver 30 min/10 min.@ Poor A -- 1.0 @25.degree.
C./120.degree. C. 3d** glass silver 30 min/10 min@ None A -- .1
@25.degree. C./120.degree. C. 3e** glass silver 30 min/10 min.@
None A -- 0.01 @25.degree. C./120.degree. C. 4y glass silver 30
min./10 min.@ Fair A 2.4:1 1.1 @25.degree. C./120.degree. C. 4z
glass silver 30 min/10 min.@ Fair A 0.6:1 1.1 @25.degree.
C./120.degree. C. 5 glass silver 2 min/30 min@ Excellent I 1:1 2.0
@25.degree. C./100.degree. C. 6 glass aluminum 5 min/20 min@ Good A
-- 2.0 @25.degree. C./100.degree. C.
__________________________________________________________________________
*A = acetone I = IPA M = MeOH ** = no acid, no water
EXAMPLE 2
In order to compare the material of British Pat. No. 1,550,532
against the present invention, the following material was prepared.
One hundred eighty gms of a silicate based polymer containing
methyltrimethoxysilane was mixed with 20 gms of Acryloid OL-42.
Acryloid OL-42 is an acrylic polymer similar to that found in the
British patent in Example 1. The Acryloid is 80% solids in
cellosolve acetate. One gram of hexamethylenetetramine catalyst was
also added with agitation.
A primer (P) was prepared for use herein which consisted of 8 gms
of HS(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3 diluted with 800 gms of
IPA, 24 gms of 40% in MeOH of ##STR11## diluted with 800 gms of
additional MeOH. Seventy-five gms of the dilute HS(CH.sub.2).sub.3
Si(OCH.sub.3).sub.3 was mixed with 25 gms of the dilute ##STR12##
and a small amount of acetic acid and water and the mixture was
stirred until clear.
A Lexan.RTM. polycarbonate slide was abraded with emery paper to
simulate an abused article from manufacturing. After the slide was
cleaned, it was measured off in 4 equal sections and marked and one
section was dipped in the solution of primer (P) from above and
then allowed to air dry for 20 minutes at room temperature.
The solution of acrylate polymer, silicate and alkoxysilane
analogous to that found in Example 1 of British Pat. No. 1,550,532
was then applied to 3/4 of the slide and the 1/4 primed area was
overcoated thereby and air dried. The coating was then cured 15
min. @70.degree. C. and 20 min. @100.degree. C. Next, 1/2 of the
slide was dipped in a solution of P and allowed to air dry for 10
minutes at room temperature. Finally, the whole slide was vapor
deposited with silver metal and cured for 15 min. @100.degree. C.
If one were to lay the slide on its edge and note the coatings or
layers on the top of the slide, the left-most 1/4 section (denoted
A) would have a silver coating only. Moving to the right, the next
1/4 section (denoted B) would have a top layer of silver covering a
layer of the British Pat. No. 1,550,532 polymer which in turn
covers the polycarbonate slide. The third 1/4 section (denoted C)
would have a top layer of silver covering a layer of P primer which
in turn covers the British Pat. No. 1,550,532 polymer which in turn
covers the polycarbonate slide. The last 1/4 section (denoted D)
consists of a top layer of silver, a second layer of the primer P,
a third layer of the British Pat. No. 1,550,532 and finally a
fourth layer of primer P.
Sections B, C, and D were scored into crosshatched squares by a
sharp instrument to give 25 equal squares. Scotch Brand adhesive
tape #650 was then pressed onto the crosshatched squares and
removed forcibly. Recognizing that the most optimum conditions were
not observed, the test was deemed to have been passed if at least
50% or more of the silver metal remained intact. Table III shows
the results.
TABLE III ______________________________________ Appearance %
Retention of Remaining Sample Pass/Fail of Silver Silver
______________________________________ B failed* 0 -- C passed 65
smooth/brilliant D passed 65 smooth/brilliant
______________________________________ *loss of adhesion occurred
at the silver/basecoat interface.
EXAMPLE 3
A silicone resin was prepared according to Examle 2 of U.S. Pat.
No. 4,173,553 with the exception that the HS(CH.sub.2).sub.3
Si(OCH.sub.3).sub.3 was present at 10 weight percent CH.sub.3
Si(OCH.sub.3).sub.3 at 40 weight percent and colloidal silica at 50
weight percent based on the weight of all three components. This
material is shown herein as "A". Another sample of silicone resin
was prepared as shown in Example 1 of U.S. Pat. No. 3,986,997, that
is, the same material as above but without HS(CH).sub.2
Si(OCH.sub.3).sub.3 and this was designated "B". The two materials
were compared side-by-side for their ability to accept and adhere
metals which were deposited thereon. Both materials were diluted to
approximately 10% solids with isopropanol.
A clean square of Lexan.RTM. polycarbonate was dipped 1/2 into "A".
The remaining 1/2 was dipped in "B". The sample was then air dried
for 40 minutes at 25.degree. C. The sample was then vapor deposited
with silver. The sample then cured 1 hour at 125.degree. C. The
samples both had excellent specularity. The samples were subjected
to a methanol rub to test the adhesion of the silver. The material
"A" was clearly superior in retaining the silver metal.
EXAMPLE 4
The silicone resin designated "B" in Example 3 above, was coated
onto a clean Lexan.RTM. polycarbonate square and cured 25 minutes
at 100.degree. C. One-half of the coated slide was then dipped into
a primer designated earlier as primer P of Example 2 and this was
allowed to dry for 2 minutes at 25.degree. C. The square was then
vapor deposited with silver and cured 1 hour at 125.degree. C. The
1/2 side of the slide that had been primed with primer P of Example
2 showed superior retention of the silver deposited thereon.
The means of metal deposition described in this specification and
claims are conventional means for depositing metals and it is
believed that elaborate descriptions of such methods are not
required by those skilled in the art.
* * * * *